Prevalence and characterization of class 1 integrons in multi-drug resistant Salmonella sp. from China in 2010

Differences in expression of genes in the MyD88 and TRIF signalling pathways and methylation of TLR4 and TRIF in Tibetan chickens and DaHeng S03 chickens infected with Salmonella enterica serovar enteritidis

Salmonella enterica serovar (S. enteritidis) is a pathogenic bacterium that can cause symptoms of food poisoning, leading to death of poultry, resulting in serious economic losses. The MyD88 and TRIF signalling pathways play important roles in activating innate and adaptive immunity in chickens infected with S. enteritidis. The objective of the present study was to characterize in vivo mRNA expressions, protein levels and methylation levels of genes in the above two pathways in both Tibetan chickens and DaHeng S03 chickens infected with S. enteritidis. MyD88-dependent and TRIF-dependent signalling pathway were activated by infection, and the MyD88 signalling pathway induced cytokines LITAF and IL-8 played important roles in fighting against the S. enteritidis infection in vivo. The TLR4 methylation might alter expression of genes involved in the MyD88 signalling pathway, and thus different breeds of chickens might show differences in susceptibility to the S. enteritidis. The increased expression of INF β was activated by S. enteritidis, but its expressions were different in levels of mRNA and protein in Tibetan chickens and DaHeng chickens, suggesting its functions on the resistance to S. enteritidis infection in chickens. This study contributes to the understanding of two pathways activated in response to S. enteritidis infection, and gives indications on the mechanisms underlying resistance of Tibetan chickens and DaHeng chickens to S. enteritidis.

Characterization of integrons and novel cassette arrays in bacteria from clinical isloates in China, 2000-2014

Rapid dissemination of antibiotic resistance genes among bacterial isolates is an increasing problem in China. Integron, a conserved DNA sequence, which is carried on episomal genetic structures, plays a very important role in development of antibiotic resistance. This systematic analysis was based on MEDLINE and EMBASE databases. We summarized the distribution and proportion of different types of gene cassette arrays of integrons (including class 1, 2, 3 and atypical class 1 integron) from clinical bacteria isolates in China. Fifty-six literatures were included in this study. Most of the strains were Gram-negative bacteria (94.1%, 7,364/7,822) while only 5.9% strains were Gram-positive bacteria. Class 1 integrons were detected in 54.2% (3956/7295) Gram-negative strains. aadA2 was the most popular gene cassette array detected from 60 Gram-positive bacteria while dfrA17-aadA5 were detected in 426 Gram-negative bacteria. This study identified 12 novel gene cassette arrays which have not been previously found in any species. All the novel gene cassette arrays were detected from Gram-negative bacteria. A regional characteristic of distribution of integrons was presented in this study. The results highlight a need for continuous surveillance of integrons and provide a guide for future research on integron-mediated bacteria resistance.